The present invention relates to a process and an apparatus which make it possible to produce a new type of composite textile structure from nonwoven fibrous sheets.
It has been proposed for decades to replace woven or knitted conventional textile sheets with so-called "nonwoven" planar textile structures consisting of elementary fibers distributed substantially in the same plane and oriented randomly in relation to each other. It is possible for such sheets to be obtained by two major general techniques, one called "dry-route technique" making use of carding, napping and similar operations, and the other called "by wet route", and derived from papermaking techniques.
It has also been proposed to produce such nonwoven sheets directly from continuous chemical filaments, as they leave their extrusion die, such a technique being nowadays commonly referred to by the expression "spun bonded".
Such elementary nonwoven sheets are often converted into more complex structures as a function of the envisaged applications, as can be seen especially from GB-A-1,600,768 and U.S. Pat. No. 2,588,228. In general, when it is desired to obtain articles exhibiting good mechanical strength both in the longitudinal direction and in the transverse direction, multilayer structures are produced into which are sandwiched reinforcing structures such as woven or nonwoven textile grids. The bonding of the reinforcing member with the nonwoven outer layers is obtained by various techniques such as, for example, mechanical interlacing (needling technique), entangling of the fibers by the action of fluid Jets (generally water), chemical bonding or heat bonding (calendering) when the elementary nonwoven sheets contain thermofusible fibers.
In the case of the nonwoven sheets obtained by a papermaking route, it has also been proposed for a long time to combine them with reinforcing structures. Such reinforcing structures may either be incorporated directly into the papermaking pulp during the manufacture or optionally incorporated between two previously produced nonwoven sheets, the bonding being in this latter case generally obtained by adhesive bonding.
In general, the techniques proposed hitherto for producing such composite structures comprising an internal reinforcement make use of a noncontinuous manufacturing cycle (separate formation of nonwoven sheets and of the reinforcement, such as grids), the assembly being carried out during a subsequent operation, and this undoubtedly increases the cost of manufacture and presents problems of storage of the elementary materials.